Mill for the production of a directly floatable fluid pulp starting from coarse minerals



3,140,056 BLE FLUID A. MOTOSI ION July 7, 1964 MILL. FOR THE PRODUCT OFA DIRECTLY FLOATA PULP STARTINGYFROM COARSE MINERALS Filed June 27, 1961In venlor ALDO no'rosi AYM Attorneys United States Patent "ice 3,140,056MllLL FOR THE PRODUCTION OF A DIRECTLY FLOATABLE FLUID PULP STARTINGFROM CQARSE MINERALS Aldo Motosi, 13 Via dei Mille, La Spezia, ItalyFiled June 27, 1961, Ser. No. 120,002 filaims priority, applicationItaly June 17, 1958 10 Claims. (Cl. 241-38) This application is acontinuation in part of abandoned application Serial No. 820,015, filedJune 12, 1959.

This invention relates to the comminution in water of solid coarse-sizedminerals (this term including sizes up to 6" or even more) and aims toprovide a mill in which the coarse minerals and the water are fedcontinuously and, at the same time, the minerals which have beencomminuted to the desired degree of fineness are continuouslydischarged, together with the overflow water, in form of a directlyfloatable fluid pulp or slurry.

The object of the invention is to provide a mill which is very compactand efiicient and which permits of accurately regulating by simple meansthe size of the particles of the comminuted minerals.

According to the invention, these ends are attained by constructing amill having a drum-like horizontal shell and a hollow rotor providedwith radial openings, rotatably mounted therein, said shell beingprovided with a hopper'for the charging of the coarse mineral and withan ascending duct provided with an adjustable overflow and with valvemeans for regulating its sectional flow area, While the interior of therotor is connected through rotary joints to a source of water and airunder pressure which are discharged through said openings in form ofradial jets which, during the revolution of the rotor, cooperate toentrain the bulk of water and minerals therein in form of a revolvingliquid belt thrown away from the rotor by centrifugal force and spacedtherefrom by a cushion of the air blown together with the water andwhich separates itself therefrom as soon as it may expand into theshell.

Due to the fact that the liquid belt is not entrained by blades dippingthereinto, the particles of water and solids assume diflierent annularspeeds. Thus the said belt of turbulent water, by entraining solids ofdiiferent sizes and weight and having different velocities, causes saidsolids to collide and rub against each other and against the walls ofthe shell and to rebounce against the rotor therein from which they arehurled again into and through the liquid belt, until they are crushed byrepeated collisions and rubbing to a suflicient fineness. When thissufficient fineness is attained, the particles of the mineral float intosaid swirling water until they reach a zone of quiet constituting theinlet end of an overflow duct from where they are discharged togetherwith the water in which they are suspended.

Further characteristic features and advantages of the mill according tothe invention will appear from the following specification in which theinvention is described with reference to the attached drawings, inwhich:

FIGURE 1 is a vertical cross section through a mill according to theinvention;

FIGURE 2 is a horizontal section taken on line IIII of FIGURE 1, and

FIGURES 3, 4 and 5 are cross sections through three modifications of themill rotor.

According to one preferred embodiment shown in FIG- URES 1 and 2, theimproved mill comprises a drum-like shell 11, supported by a base B, andprovided with a hopper 13, through which the coarse-sized mineral to beground is fed into the mill.

At one side of said hopper a duct 26-126 is formed,

3,148,855 Patented July 7, 1964 having an ascending branch 26 extendingslightly above the nearest inner drum Wall and provided with a throttlevalve 27 or equivalent means and a descending branch 126 connected tothe ascending branch at a point below the hopper top and provided by itslower end with an outlet 29. In practice, the ducts 26 and 126 may beformed by attaching to the hopper Wall a vertical partition 28 extendingfrom underneath the inlet end of said duct 26, preferably above thelevel of the outlet 29. Said partition 28 is provided with a verticallymovable extension constituted by a pair of parallel partitions 128attached to a threaded stem 228 which may be axially shifted by means ofa wing nut 328 rotatably but not axially shiftable mounted on a fixedpart of the said hopper. Thus the ducts 26 and 126 constitute a kind ofadjustable overflow duct, the two branches of which are separated by akind of sluice valve 28-128 the height of which determines the height ofthe liquid in the hopper 13.

Through two openings formed in the bottoms on the said drum 11 a shaft15 is rotatably mounted.

In a central portion of said shaft, a tubular rotor 14 is mounted on aplurality of supporting members 16 fastened radially to the shaft 15.The rotor proper 14 is a tubular member provided with rows of radialperforations or slits 19 and preferably, but not necessarily, with veryshort projecting bars 18 extending longitudinally of the rotor, so as toremain well spaced from the drum interior.

The rotor 14 communicates axially with a pair of fluid feed chambers 25fastened by their inner ends to the heads of the drum, the outer end ofsaid chambers being provided with conventional wear sleeves 30 andstuffing boxes 32 in which the shaft 15 revolves with a fluidtight fit.The chambers 25 are provided with valved ports or nipples 31 and 131through which the fluids (water, chemicals, if any, and air) which arenecessary for performing the process of the invention are fed. In theexample as shown, air may be fed with suitable pressure through the port131. The mill shell is usually provided with the conventional liner,which, in the examples as shown is in the form of spaced bars 23.

The operation of the mill is as follows: The mill is first run byfeeding therein, through the rotor 14, some water which is sprayedthrough the slits 19 into the drum 11 until its level rises into saiddrum substantially at its overflow level. Together with the water (whichmay contain some chemicals, if required) also some air may be fed, inorder to create an air-filled space at the central portion of the mill,inside an annular belt of water thrown by centrifugal force away fromthe rotor 14. Then the coarse material to be ground finely is fed intothe hopper 13 and allowed to fall in the direction of the rotor 14 whichthrows by centrifugal force both solids and the liquid coming intocontact therewith towards and through the annular belt of water, wherethey encounter other fragments of solid materials and finally the shellwalls or liner. At the same time, the jets of water projected with greatforce through the openings or slits 19 and revolving with the rotor, byacting upon the inner surface of the belt of water, entrain said waterand the solids therein into rotation, but at different velocities. Thusa combination of repeated rubbing and impact of the materials betweenthem and against the mill and rotor walls takes place inside the mill,in which the coarse solid material is reduced to the required fineness.

The operation of this mill is a continuous one, that is the solidmaterial to be ground is fed at a rate determined by experiments and atthe same time water and some air are fed into the mill across the rotoropenings and at the same time the water charged with ground material ofthe required fineness or pulp flows upwardly through the ascendingbranch of duct 26, overflows the partition 128 and flows down throughthe descending duct 126 until it is discharged through the outlet 29.The pulp may be fed directly to a flotation equipment-for separation ofits valuable parts from the gangue.

The fineness of thepulp may be exactly regulated by suitably adjustingthe rate of feed of the liquid, the height of the overflow 28, 128 andthe free passage area of the ascending branch of duct 26. In fact, byleaving all other conditions unaltered, it is evident that the finenessof the ground material entrainedby the overflow water will be inverselyproportional to the velocity of the ascending water flow in the duct 26and thus by throttling more or less the, ascending branch 26 of thisduct by means of valve 27, FIG. 1, the fineness of the discharged fluidpulp may be exactly regulated.

As said in the preamble, experience has shown that, in order that millmay operate ,as described, the belt of water should not be entrainedinto rotation by long bladelike members projecting out of the rotorsurface radially thereinto. Onthe contrary the projecting parts of therotor-if anyshould be well spaced from the drum interior as to come tobe almost always inside of the inner surface of the water belt.

Although in FIGURE 1 the rotor 14 is shown provided with projecting bars18, these bars may be completely omitted or replaced by channels 118(FIGURE 3) grooves, flutings and even-a roughened surface.

In FIGURE 4, as variation, there is shown, a cylindrical rotor 14mounted eccentrically on its shaft 15.

In FIGURE 5, the rotor 214 is elliptical.

In any case, it is to be understood that the most projecting parts ofthe rotor must be such that their distance from the nearest part of thedrum interior is less than the size of the coarsest material to be fedinto the mill.

Furthermore the rotor 14 is usually mounted in the drum eccentrically,as in the case as shown, in which the drum shell 11 is substantiallyspiral-shaped.

All the above and other possible embodiments of the invention should besuch as to promote the formation of a water belt, containing the solidsto be comminuted in it and spaced, at least in part, from the rotor, byan air cushion, the whole in order to avoid that the liquid and solidparts forming the belt revolve at substantially the same angular speedor conversely in order to cause the solids in the belt to revolve atdifferent angular speeds, according to their different weights andposition in the liquid belt, thus tending to impact or rub-against eachother and the drum walls, or the lining bars thereof.

I claim:

1. A mill for the continuous production of a directly floatable fluidpulp starting from coarse-sized solid materials, comprising adrum-likeshell, a feed hopper for solid materials opening into the extendingabove said shell, a hollow rotor journaled for rotation within saidshell and having a peripheral surface spaced from the shell, radialthrough-openings in the peripheral surface of said rotor communicatingwith the hollow interior thereof, means for feeding aqueous fluids intosaid hollow rotor and through said radial openings into said shell,means for rotating said rotor at high angular speed, and an ascendingoverflow duct opening into and extending above said shell.

2. A mill according to claim 1, in which the rotor is provided withshort parts projecting from its peripheral surface and which are spacedfrom the shell interior by more than the maximum size of the material tobe comminuted.

3. A mill according to claim 1, in which the rotor is provided withlongitudinalgrooves.

:4. A mill according to claim 1, in which the rotor is elliptical incross section.

5. A mill according to claim 1, comprising means for adjusting theheight of the overflow duct.

6. A mill according to claim 1 wherein is additionally provided ductmeans for collecting and discharging the fluid overflowing from saidoverflow duct.

7. A mill according to claim 1 in which the rotor is jurnaled forrotation about a horizontal axis eccentrically positioned with respectto said shell, the peripheral surface of said rotor being spaced at allpoints from the shell by a distance that is greater than the maximumsize diameter of the material to be comminuted.

8. A mill according to claim 1 wherein said radial through-openings havesmall diameters sutficient only to pass aqueous fluids but too small topass the solid material to be comminuted.

9. A mill for the continuous production of a directly floatable fluidpulp starting from coarse-sized solid materials, comprising a drum-likeshell, a feed hopper for solid materials opening into and extendingabove said shell, a hollow rotor journaled for rotation within saidshell and having a peripheral surface spaced from the shell, radialthrough-openings in the peripheral surface of said rotor communicatingwith the hollow interior thereof, means for feeding aqueous fluids intosaid hollow rotor and through said radial openings into said shell,means'for rotating said rotor at high angular speed, and an ascendingoverflow duct opening into said shell, said overflow duct comprising anupright, partition wall within the hopper extending downwardly to alevel slightly within the confines of the shell, a second upright wallwithin the hopper substantially parallel to said first wall andextending upwardly from a level in the lower part of said hopper, asluice valve-like member coacting with the top part of said secondupright wall to extend it upwardly, said sluice member having a top edgewhich constitutesthe top of said overflow duct, and means for shiftingsaid sluice valve member vertically so as to lift and lower its topedge, said hopper having an opening in its side opposite said secondpartition wall for discharging fluid overflowing from said overflowduct.

10. A mill according to claim 9 in which valve means are provided in thesaid overflow duct for constricting its free flow area.

UNITED STATES PATENTS References Cited in the file of this patent1,780,845 Sherwood Nov. 4, 1930 2,656,119 Shelton et al. Oct. 20, 19532,914,259 Hestvik et a1. Nov. 24, 1959 3,030,037 Raetz Apr. 17, 19623,038,669 Lykken et al. June 12, 1962 FOREIGN PATENTS 581,986 CanadaAug. 25, 1959

1. A MILL FOR THE CONTINUOUS PRODUCTION OF A DIRECTLY FLOATABLE FLUIDPULP STARTING FROM COARSE-SIZED SOLID MATERIALS, COMPRISING A DRUM-LIKESHELL, A FEED HOPPER FOR SOLID MATERIALS OPENING INTO THE EXTENDINGABOVE SAID SHELL, A HOLLOW ROTOR JOURNALED FOR ROTATION WITHIN SAIDSHELL AND HAVING A PERIPHERAL SURFACE SPACED FROM THE SHELL, RADIALTHROUGH-OPENINGS IN THE PERIPHERAL SURFACE OF SAID ROTOR COMMUNICATINGWITH THE HOLLOW INTERIOR THEREOF, MEANS FOR FEEDING AQUEOUS FLUIDS INTOSAID HOLLOW ROTOR AND THROUGH SAID RADIAL OPENINGS INTO SAID SHELL,MEANS FOR ROTATING SAID ROTOR AT HIGH ANGULAR SPEED, AND AN ASCENDINGOVERFLOW DUCT OPENING INTO AND EXTENDING ABOVE SAID SHELL.